The Cliffs of Undalar were a steep rock-face located on Bajor, with a unique fungus growing on them.

In 2372, Keiko O'Brien wanted to rappel down the cliffs of Undalar to retrieve a fungus sample for her studies, but Miles wouldn't let her, reminding her that she was pregnant and that it would be too dangerous for her. He later cited this to CommanderDax as an example of her acting more reckless than she should when she is pregnant. (DS9: "Body Parts")